The CEO of Volkswagen, Martin Winterkorn, apologized over the weekend, following the EPA's order that 500,000 Volkswagen and Audi vehicles in the U.S. be recalled due to software that kicks in emissions regulation systems in cars -- but only when the car is being tested for emissions.

"I personally am deeply sorry that we have broken the trust of our customers and the public," Winterkorn said in a statement.

But investors weren't impressed with the apology, sending Volkswagen shares down as much as 23 per cent Monday. That would have wiped C$23 billion off the market value of Volkswagen.